It is frequently required to enclose an elongated structure in a housing or confinement duct, for example to be able to monitor possible leakage from a pipe in highly sensitive operations where such leakage which may result in environmental contamination or the development of a dangerous situation.
For example, a pipe carrying a radioactive material may be surrounded by a secondary confinement pipe so that any products leaking into the space between the primary conduit and the secondary pipe may be detected by sensors provided in such space.
Alternatively, it may be advantageous to monitor leakage from the environment into a protected space around an elongated member such as an electrical conductor.
In still another application of a secondary confinement pipe, a primary conduit carrying a gas may be surrounded by the secondary confinement pipe so that any leakage of gas into the space around the primary conduit can be detected.
In all such cases, it is advantageous to utilize a relatively rigid secondary confinement pipe structure.
While ordinary rigid polyvinylchloride pipe can be utilized for this purpose when the primary conduit or elongated member can be fed through the secondary confinement pipe, in many cases it is necessary to assemble the secondary confinement pipe around the preexisting primary conduit or elongated member. Accordingly, snap-together constructions have been provided in which parts of the secondary confinement pipe can be interfitted around the primary conduit to fully enclose the latter. One of the problems with such secondary confinements is that of sealing of the joints between the interfitting parts of the secondary confinement pipe.
Customarily separate sealing members or packings were required for this purpose. Such sealing arrangements were not economical and, in many cases, did not function efficiently. While the problem could be solved by forcing a sealant into gaps at the joints, in practice this is a time-consuming operation and depends on the precision of the workmanship for effective sealing.